Rules and guidelines are provided for subject indexing in the ERIC system. The principle of "subject access" is discussed with particular reference to "coordinate indexing," which involves designating subject content by unit terms (or tags) that may be put together or "coordinated" for subsequent retrieval. The nature of educational literature and the characteristics of educational community user groups are delineated in order to place ERIC indexing in proper perspective. Indexing tools necessary for the ERIC indexing process are also described. Detailed guidelines are presented on the indexing process itself, involving: (1) examination of the document; (2) identification of indexable information, e.g., population characteristics (including educational level), document form/type, curriculum or educational subject/field, activity, methodology, and materials; (3) translation and negotiation of indexable concepts into approved terminology, i.e., ERIC Descriptors and Identifiers. Additional guidance is offered on several special indexing issues, including specificity of indexing, weighting (major/minor terms), over- and under-indexing, and the indexing review process. (JH)